Realization of a wearable miniaturized thermoelectric generator for human body applications

This paper presents the realization of a full-fledged wearable miniaturized thermoelectric generator (TEG) specifically engineered for human body applications. It is based on a surface micromachined poly-SiGe thermopile. In view of the adverse thermal environment on human body, special attention is paid to the optimal design for the individual thermocouple, for the thermopile featured with a rim structure standing out of Si substrate, and for the wearable TEG. Fabricated by using surface micromachining technology, each thermopile chip contains 2350 or 4700 thermocouples connected thermally in parallel and electrically in series. The effectiveness of the targeted design is validated by both simulation and experiments. To facilitate further packaging, the thermopile chip is flip-chip bonded to a Si chip coated with a thin layer of BCB. Such a bonded thermopile chip delivers an open-circuit output voltage of 12.5 V/(K cm2) and an output power of 0.026 μW/(K2 cm2) on a matched external load. Towards the making of a full-fledged wearable TEG, the bonded thermopile chip is manually assembled with other specially designed components. Being worn on human body, the wearable TEG delivers an open-circuit output voltage of about 0.15 V and an output power of about 0.3 nW on a matched external load. Further improvement in the output performance can be achieved by optimizing material properties, applying metal-to-metal bonding and fabricating thermocouple microstructures on high topography.